This invention relates to a fuel filter of an internal combustion engine, in particular of a diesel engine, with a filter housing having an operationally lower housing base and an upper, removable housing cover, with one raw fuel inlet and pure fuel outlet each being provided in the filter housing, with a replaceable ring filter insert being arranged in the filter housing through which the fuel can flow radially from the outside to the inside, said ring filter insert subdividing an interior of the filter housing into a raw area and a pure area, with a support body being arranged in the interior of the ring filter insert through which extends a first flow channel being connected, on the one hand, with the pure area and, on the other hand, with the pure fuel outlet, and a second flow channel being connected, on the one hand, with the raw area via a vent throttle or a vent valve and, on the other hand, with a tank return in the filter housing.
A fuel filter of the aforementioned type is known from DE 60 2004 006 277 T2. With this fuel filter, the raw fuel inlet is provided either on the bottom at the circumference or at the lower end wall of the filter housing. With this fuel filter, the support body is designed in two parts, with a radially outer part of the support body forming one part of the filter insert and a radially inner part of the support body forming one part of the filter housing. The fuel to be cleaned flows from the bottom to the top around the outer circumference of the filter insert and then flows through the filter insert radially from the outside to the inside. The cleaned fuel flows near the upper end of the support body into its central flow channel and through it to the pure fuel outlet. For venting the filter housing, a vent throttle is used in an upper end disk of the ring filter insert, with the raw area of the housing being in flow connection with the second flow channel via the vent throttle. On the other hand, the second flow channel in the support body is in flow connection with a tank return.
It is to be considered disadvantageous with this known fuel filter that the separation of water droplets entrained in the fuel is rendered more difficult due to the flow of the fuel to be cleaned from the bottom to the top at the outer circumference of the filter insert.
Another fuel filter is known from the document U.S. Pat. No. 5,922,199 A. This fuel filter is designed as a hanging cup system, wherein a cup-shaped housing is screwed as a bottom part onto a base here forming the upper part of the fuel filter. Maintenance of the fuel filter is here only possible from the bottom by unscrewing the hanging cup. In this case, fuel disadvantageously always remains in the cup which may easily result in pollution and renders it difficult to change the filter insert.